Real part of the refractive index, specifically the refractive index decrement δ of breast tissues and substitute materials listed in Table I . For microcalcifications, calcium carbonate and aluminum were found to straddle the refractive index decrements of calcium oxalate and calcium hydroxyapatite in the energy range of 5–50 keV.
Linear attenuation coefficient μ that is related to the imaginary part of the refractive index β by , where λ is the wavelength corresponding to energy E is shown.
Three tissue substitute materials exhibited δ and μ values between that of adipose and fibroglandular breast tissue over at least 50% of the energy range considered are shown. With the exception of BR10 over the narrow range or 30–35 keV, the equivalent fibroglandular fraction of δ and μ were substantially different.
For the five materials that exhibited increased δ(E) over fibroglandular tissue, (a) the percent increase in δ(E), and (b) the percent difference in μ(E) with respect to fibroglandular tissue are shown. The percent difference in μ(E) with respect to fibroglandular tissue is energy-dependent.
Substitute materials for breast tissues are ranked in order of their absolute difference in δ from the target breast tissue over the energy range of 5–50 keV. For each target breast tissue in column 1, the reference source for elemental composition is provided in column 2. For each substitute, the material, reference source for elemental composition or the molecular formula, mean ± standard deviation in % δdiff over the energy range, and the % δdiff range [minimum, maximum] are provided.
Equivalent fibroglandular weight fraction (f g ) in terms of δ for seven tissue substitute materials that exhibited δ(E) between that of adipose and fibroglandular breast tissue over the energy range of 5–50 keV. For each tissue substitute material, the mean, the standard deviation, the minimum, and the maximum of f g over 5–50 keV are provided.
Percent difference in refractive index decrement computed with respect to fibroglandular tissue for materials that exhibited increased δ(E) over fibroglandular tissue in the energy range of 5–50 keV.
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